The elucidation of the possible relationship between glycoconjugate levels and profiles (gangliosides in particular) of two rat mammary tumors (SMT-2A and MT-W9a) and the formation of metastasis is the goal of this project. SMT-2A tumor metastasizes very extensively to different organs in rats, including lungs, whereas MT-W9a does not metastasize under experimental conditions. It has been observed that SMT-2A contains about 3.5-fold more lipid-bound sialic acid than nonmetastasizing MT-W9a tumor per 100 mg of lipid extracted. Also, the ganglioside pattern of these two tumors is different. SMT-2A tumors contain relatively higher quantities of two disialongangliosides, GD2 and GD1b, trisialoganglioside GT1b and tetrasialoganglioside GQ1b. On the other hand MT-W9a contains relatively and absolute more monosialohematoside GM3. The relative amounts of monosialoganglioside GM1 and disialohematoside GD3 are also higher in MT-W9a. Analyses of gangliosides from lungs of SMT-2A-bearing rats (54 days postimplantation), containing large numbers of macroscopic metastatic nodules, reveal that the level of lipid-bound sialic acid may be up to 4-fold higher than in normal lungs and may be even higher than in SMT-2A primary tumors. The level of lipid-bound sialic acid in larger excised lung nodules (occasionally found) and secondary tumors from axillary lymph nodes are approximately 2-fold higher than in primary SMT-2A tumors. All this very strongly suggests that primary tumor cells (or clumps of cells) with a relatively higher content of gangliosides than average may more effectively originate metastatic (secondary) tumors. Investigation of the content and profile of gangliosides in isolated tumor plasma membranes shows that plasma membranes are enriched in total ganglioside content as compared with whole cells. The degree of enrichment in SMT-2A plasma membranes is 1.8-fold and in MT-W9a, 3.1-fold. The total ganglioside content in plasma membranes from metastasizing tumor SMT-2A is 1.8-fold higher than in plasma membranes from nonmetastasizing tumor MT-W9a.